GB2284712A - Antenna - Google Patents
Antenna Download PDFInfo
- Publication number
- GB2284712A GB2284712A GB8709762A GB8709762A GB2284712A GB 2284712 A GB2284712 A GB 2284712A GB 8709762 A GB8709762 A GB 8709762A GB 8709762 A GB8709762 A GB 8709762A GB 2284712 A GB2284712 A GB 2284712A
- Authority
- GB
- United Kingdom
- Prior art keywords
- antenna
- reactive components
- capacitors
- length
- transmission line
- Prior art date
- Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
- Granted
Links
- 239000003990 capacitor Substances 0.000 claims description 16
- 230000005540 biological transmission Effects 0.000 claims description 6
- 238000000926 separation method Methods 0.000 description 3
- 238000010586 diagram Methods 0.000 description 2
- 230000005404 monopole Effects 0.000 description 2
- 230000000694 effects Effects 0.000 description 1
- 230000001939 inductive effect Effects 0.000 description 1
- 238000005259 measurement Methods 0.000 description 1
Classifications
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q3/00—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system
- H01Q3/24—Arrangements for changing or varying the orientation or the shape of the directional pattern of the waves radiated from an antenna or antenna system varying the orientation by switching energy from one active radiating element to another, e.g. for beam switching
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01Q—ANTENNAS, i.e. RADIO AERIALS
- H01Q9/00—Electrically-short antennas having dimensions not more than twice the operating wavelength and consisting of conductive active radiating elements
- H01Q9/04—Resonant antennas
- H01Q9/30—Resonant antennas with feed to end of elongated active element, e.g. unipole
- H01Q9/42—Resonant antennas with feed to end of elongated active element, e.g. unipole with folded element, the folded parts being spaced apart a small fraction of the operating wavelength
-
- H—ELECTRICITY
- H03—ELECTRONIC CIRCUITRY
- H03J—TUNING RESONANT CIRCUITS; SELECTING RESONANT CIRCUITS
- H03J5/00—Discontinuous tuning; Selecting predetermined frequencies; Selecting frequency bands with or without continuous tuning in one or more of the bands, e.g. push-button tuning, turret tuner
- H03J5/24—Discontinuous tuning; Selecting predetermined frequencies; Selecting frequency bands with or without continuous tuning in one or more of the bands, e.g. push-button tuning, turret tuner with a number of separate pretuned tuning circuits or separate tuning elements selectively brought into circuit, e.g. for waveband selection or for television channel selection
Landscapes
- Variable-Direction Aerials And Aerial Arrays (AREA)
- Support Of Aerials (AREA)
- Details Of Aerials (AREA)
Abstract
An antenna comprising a plurality of reactive components connected in parallel and spaced along the length of the antenna and switch means associated with the reactive components to enable selected ones thereof to be brought into circuit. This enables rapid tuning of the antenna over a wide frequency range e.g. for frequency-hopping. <IMAGE>
Description
This invention relates to antennas which are electrically small and are brought to resonance by loading with reactance. Such antennas are often described as 'transmission line antennas'. By 'electrically small' it is meant that the length of the antenna is small compared with 2 or k of the wavelength ( A ) of the signal to be transmitted i.e. small in comparison to a 2-wave dipole or -wave monopole. For example, an antenna of length > /10 would be considered to be electrically small. The present invention relates primarily to VHF antennas. The Hula Hoop, which is an antenna in the shape of a child's hula hoop is one known example of an electrically small antenna tuned by a capacitor at one end.
Fig.l shows a typical known arrangement of a transmission line antenna 10. In this example a shunt feed 12 is used to match the antenna to its transmitter. A variable capacitor 14 positioned in parallel at the open end of the transmission line is used to tune the antenna 10.
When an antenna is intended to operate over a wide frequency range and at high power, the loading capacitor has to handle large currents and may have to be a gas-filled or vacuum variable type.
Such components can be very accurately set but require a mechanical drive and cannot be tuned very rapidly. The precision required in setting such a component prevents its replacement by a bank of fixed capacitors and switches since it is not possible to provide sufficiently small fixed capacitances, typically as small as 0.1 pico
Farad, to enable the required degree of precision to be achieved.
It is also known to provide a tuning arrangement in a transmission line antenna consisting of several variable capacitors located along the length of the antenna and connected in series. This known arrangement has proved impractical - in particular it is difficult to access the capacitors for tuning.
According to the present invention we provide an antenna ccrSnislng a plurality of reactive components connected in parallel and spaced along the length of the antenna, the reactive components being associated with switch means enabling selected ones thereof to be brought into circuit.
Preferably the reactive components comprise fixed value capacitors.
The arrangement defined above can be designed to provide several overlapping, narrow, operating bands covering the complete frequency range of a particular antenna.
Particular embodiments of the present invention will now be described with reference to figures 2-5 of the accompanying drawings, each of which shows an antenna according to a different embodiment of the present invention.
In figure 2 a transmission line antenna in the form of a monopole is indicated generally at 15 and has a shunt feed 16. A bank of capacitors C1 - Cn are connected in parallel between the horizontal portion of the antenna 15 and ground by switches S1 - Sn. Each capacitor together with its connected vertical wires provides a reactance made up of capacitative and inductive elements, the net reactance being capacitative. The e electrical separations ( n & n of the capacitors are indicated in figure 2, i.e. the separation of each pair of capacitors in terms of the wavelength (a) of the signal being transmitted i.e. e = 2"1/3 where t is the physical length of the antenna. In use, different ones of the switches S1 Sn are selected to tune the antenna according to the frequency of the signal being transmitted. In practice, the selection of individual ones or combinations of the switches S1 - 5n may be computer controlled.
Alternatively, switch selection may be achieved by a control system utilising RF measurements.
If all of the capacitors C1 - Cn are of equal value, those nearest the feed end of the antenna 15 will have much less effect in reducing the resonant frequency than those at the open end of the antenna. Therefore, greater precision can be obtained by placing capacitors near to the feed end of the antenna and it may be desirable for capacitors to be connected to the vertical portion of the antenna as shown in figure 3.
The invention can also be applied to antennas which are not straight such as the arcuate antenna shown in figure 4 or the helical antenna shown in figure 5 the top loading of which is in helical form.
It should be understood that matching arrangements other than the shunt feeds shown in the diagrams can be used in antennas according to the invention. In addition the antenna may be of balanced form as well as of the unbalanced forms as shown in the diagrams.
The capacitors C1 - Cn may have different capacitances and the electrical separations & 1 - n may be varied as desired.
The present invention has the advantage that it enables very fast tuning of an antenna to be carried out e.g. as needed for frequency hopping radios used in military applications.
Claims (4)
1. An antenna comprising a plurality of reactive components connected in parallel and spaced along the length of the antenna and switch means associated with the reactive components to enable selected ones thereof to be brought into circuit.
2. An antenna according to claim 1 wherein the reactive components comprise fired value capacitors.
3. An antenna according to claim 1 or claim 2 in the form of a transmission line antenna.
4. An antenna substantially as herein described with reference to, and as illustrated in, any one of figures 2 to 5 of the accompanying drawings.
Priority Applications (4)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8709762A GB2284712B (en) | 1987-04-24 | 1987-04-24 | Antenna |
| IT8847862A IT8847862A0 (en) | 1987-04-24 | 1988-04-18 | ANTENNA |
| FR8805326A FR2717310A1 (en) | 1987-04-24 | 1988-04-22 | Antenna. |
| SE8801533A SE8801533D0 (en) | 1987-04-24 | 1988-04-22 | ANTENNA |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| GB8709762A GB2284712B (en) | 1987-04-24 | 1987-04-24 | Antenna |
Publications (3)
| Publication Number | Publication Date |
|---|---|
| GB8709762D0 GB8709762D0 (en) | 1995-03-15 |
| GB2284712A true GB2284712A (en) | 1995-06-14 |
| GB2284712B GB2284712B (en) | 1995-10-11 |
Family
ID=10616309
Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| GB8709762A Expired - Fee Related GB2284712B (en) | 1987-04-24 | 1987-04-24 | Antenna |
Country Status (4)
| Country | Link |
|---|---|
| FR (1) | FR2717310A1 (en) |
| GB (1) | GB2284712B (en) |
| IT (1) | IT8847862A0 (en) |
| SE (1) | SE8801533D0 (en) |
Cited By (4)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0851533A1 (en) * | 1996-12-31 | 1998-07-01 | Nortel Networks Corporation | An inverted-E antenna |
| GB2371924A (en) * | 2001-02-01 | 2002-08-07 | Nokia Mobile Phones Ltd | Capacitive antenna tuning |
| EP1787354A2 (en) * | 2004-06-21 | 2007-05-23 | Motorola, Inc. | Multi-frequency conductive-strip antenna system |
| WO2014206085A1 (en) * | 2013-06-28 | 2014-12-31 | Li Ping | Resonant broadband short-wave antenna |
-
1987
- 1987-04-24 GB GB8709762A patent/GB2284712B/en not_active Expired - Fee Related
-
1988
- 1988-04-18 IT IT8847862A patent/IT8847862A0/en unknown
- 1988-04-22 SE SE8801533A patent/SE8801533D0/en not_active Application Discontinuation
- 1988-04-22 FR FR8805326A patent/FR2717310A1/en not_active Withdrawn
Cited By (7)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0851533A1 (en) * | 1996-12-31 | 1998-07-01 | Nortel Networks Corporation | An inverted-E antenna |
| US6025805A (en) * | 1996-12-31 | 2000-02-15 | Northern Telecom Limited | Inverted-E antenna |
| GB2371924A (en) * | 2001-02-01 | 2002-08-07 | Nokia Mobile Phones Ltd | Capacitive antenna tuning |
| EP1787354A2 (en) * | 2004-06-21 | 2007-05-23 | Motorola, Inc. | Multi-frequency conductive-strip antenna system |
| EP1787354A4 (en) * | 2004-06-21 | 2009-02-18 | Motorola Inc | Multi-frequency conductive-strip antenna system |
| US7928914B2 (en) | 2004-06-21 | 2011-04-19 | Motorola Mobility, Inc. | Multi-frequency conductive-strip antenna system |
| WO2014206085A1 (en) * | 2013-06-28 | 2014-12-31 | Li Ping | Resonant broadband short-wave antenna |
Also Published As
| Publication number | Publication date |
|---|---|
| SE8801533D0 (en) | 1988-04-22 |
| GB2284712B (en) | 1995-10-11 |
| GB8709762D0 (en) | 1995-03-15 |
| FR2717310A1 (en) | 1995-09-15 |
| IT8847862A0 (en) | 1988-04-18 |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| PCNP | Patent ceased through non-payment of renewal fee |
Effective date: 19960111 |